Control valve for air compressor systems



Aug. 18, 1953 M. J. CADY 2,649,241

CONTROL VALVE FOR AIR COMPRESSOR SYSTEMS Filed May 16, 1951 fmz/eiazfor lqalcalw zffiay/ y M, M azgw Patented Aug. 18, 1953 OFFICE CONTROL VALVE FOR AIR COMPRESSOR SYSTEMS Malcolm J. Oady, Stoughton, Mass.

Application May 16, 1951, Serial No. 226,662

3 Claims. (01. 230-31) This invention relates to an air compressor system and more particularly to a valve device for preventing the return flow of compressed air from a receiver to a compressor when the compressor has ceased to deliver compressed air.

While heretofore valves of the type commonly known as check valves have been installed, for this purpose, in the compressed air discharge line leading from the compressor to the receiver, such valves have taken the form of aflap movable toward and away from a seat and exposed on one face to the pulsating pressure exerted by the compressed air delivered from the compressor at each stroke thereof and on the other face to the opposing pressure exerted by the tendency of the compressed air in the receiver to return toward the compressor. The violent chattering of the flap of the check valve on its seat caused by these opposing pressures has resulted not only in a constant undesirable noise during operation of the compressor but also in a very rapid deterioration and destruction of the valve necessitating frequent and costly replacements and entailing constant supervision and loss of time and labor in maintenance.

The principal object of the present invention is to provide a valve device of the character described which will effectively and efficiently prevent the return flow of compressed air from the receiver when the compressor has ceased to deliver compressed air and which, at the same time, completely eliminates any chattering of the valve on its seat thereby to do away with the aforementioned disadvantages of the valves heretofore used and to result in a device which is substantially noiseless in operation and which can be utilized over long sustained periods of service without requiring replacement or maintenance. Other objects of this invention are to provide a valve device of the character described which is of simple and durable construction, inexpensive to manufacture, economical in operation, and which may be readily installed in all conventional air compressor systems with minimum adjustment and expense.

Other objects and advantages will be apparent from a consideration of the following description and the accompanying drawings wherein Fig. 1 is a diagrammatic representation of a conventional air compressor system showing the valve device installed therein;

Fig. 2 is an enlarged vertical section through the center of the valve device of Fig. l and showing the valve in closed position; and

Fig. 3 is a section similar to Fig. 2 but showing the valve in open position.

Referring to Fig. 1 of the drawings, the numeral l designates an air compressor here shown, by way of example, as a two-stage air compressor of a conventional commercial type from which a compressed air discharge conduit 2 leads in the customary manner to a compressed air receiver 3. The first stage cylinder head 4 of the compressor is provided with a suction valve of the ordinary commercial type (not shown) which when open provides free communication between the interior of the cylinder and the atmosphere through a port. The second stage cylinder head 5 is also provided with a suction valve (not shown) of the ordinary commercial type. The suction valves are normally open during the suction stroke of the respective cylinders of the compressor and closed during the discharge stroke but when it is desired to cause the compressor to cease delivery of compressed air through the discharge conduit without stopping the compressor, the suction valves are held open during the discharge stroke of the respective cylinders. An unloader pressure conduit 6 leads from the receiver to the suction valves and is provided with a three-way release valve l of well known commercial construction which normally opens the portion 8 of the unloader pressure conduit between said valve 7 and suction valves of the compressor to the atmosphere through the port 9 and closes the portion ill of the unloader pressure conduit between said valve 1 and the receiver and which is responsive to a predetermined maximum pressure within the receiver to open said portion Ill and to close the port 9 thereby to permit said pressure from the receiver to pass through the portion 8 of the unloader pressure conduit to the suction valves. In accordance with conventional compressor systems, while atmospheric pressure exists in the portion 8 of the unloader pressure conduit the suction valves are permitted to close during the discharge stroke of the respective cylinders but when said pres sure from the receiver is admitted into said portion 8, the suction valves are forced to open and to remain open during the discharge stroke of the respective cylinders.

With reference to Figs. 2 and 3, a valve device I3 is provided with a valve body i4 having a compressed air inlet chamber l5 and a compressed air discharge chamber l6 separated by a partition I! defining a valve seat 18. The valve body is interposed in the compressed air discharge conduit 2 intermediate the compressor and receiver. For this purpose, the inlet chamber i5 is formed with an outwardly projecting portion l9 provided with an internally screw normal to the portion 2| and provided with an internally screw threaded opening 24 adapted to receive one end of an annular spacer 25. The opposite end of the spacer is externally threaded to receive the base of a bonnet 26 and is further provided with an annular recess 2? to accommodate an annular reduced portion 28 of a plate 29. The plate is held in fixed position upon the spacer by the shoulder 38 formed in the bonnet and is formed with a central opening 3! to slidably accommodate a piston rod 32. On its inner face the plate is formed with a further reduced portion 33 constituting a back valve seat as Will hereinafter be more fully described.

One end of piston rod 32 is movably disposed in the compressed air discharge chamber l6 and is formed with a front valve head 35 adapted to seat on the valve seat It and an inwardly spaced rear valve head 38 adapted to seat'on the "back valve seat of the plate 29, the parts being so constructed and arranged that when the front valve head 35 is seated the rear valve head 3!} is unseated and when the front valve head 35 is unseated the rear valve head 35 is seated.

The bonnet 26 is formed with a central air pressure chamber 37 and slidably accommodates therein a piston 38 fixedly secured on the opposite end of piston rod 32 by suitable means here shown by way of example as a nut 39, the piston being formed with spaced piston rings 49.

The opposite outer end 41 of the bonnet is formed with a central internally threaded opening 42 to receive the nipple of a coupling 63, the coupling in turn receiving one end of an air conduit M. The opposite end of the air conduit is connected to the portion 8 of the unloader pressure conduit 6 as shown in Fig. 1.

As is customary in air compressor systems, a pressure relief valve 45 of a conventional commercial type is provided in the compressed air discharge conduit 2 on the compressor side of the valve device [3, a imilar pressure relief valve 46 is provided in the receiver and a manually operated stop valve 47 is provided in the compressed air discharge conduit 2 on the receiver side of the valve device [3.

In describing the operation of the above valve device, it will be assumed that the pressure of compressed air within the receiver has fallen to a predetermined minimum, the three-way release valve 1 responsive to said pressure has opened the portion 8 of the unloader pressure conduit to the atmosphere through port Q and closed the portion H], the suction valves are now permitted to close during the discharge stroke of the cylinders of the compressor and the compressor is therefore delivering compressed air through the compressed air discharge conduit 2. Because the air pressure chamber 37! of the 'valve device 13 is in communication with the portion 8 of the unloader pressure conduit through the air conduit 44, atmospheric pressure now exists in said chamber 31.

into the compressed air inletchamber l5 of the valve body overcomes the pressure of the return flow of compressed air from the receiver acting upon the rear face of the front valve head 35, said front valve head 35 is unseated to permit the flow of compressed air into the compressed air discharge chamber l6 and thence to the receiver 3 through the compressed air discharge conduit 2. At the same time therear valve head 36 is seated on the back valve seat of the plate 29 thereby to prevent the flow of compressed air into the air pressure chamber 31. The unseating movementof the front valve head 35 transmitted to the piston 38 within the air pressure chamber through the piston rod 32 is unopposed since, as above described, only atmospheric pressure exists in said air pressure chamber. It will thus be evident that during the delivery of compressed air through the discharge conduit 2, the valve heads 35 and 36 are subjected to the pulsating pressure of the compressed air being delivered from the compressor but are opposed only by atmospheric pressure within the air pressure chamber 31, thereby to create an unbalanced condition and to eliminate all chattering of the valve heads on their respective seats.

When the pressure within the receiver reaches a predetermined maximum the three-Way release valve 1, in response to said pressure, opens the portion ll) of the unloader pressure conduit, closes the port 9 and permits said pressure to pass through the portion 8 of the unloader pressure conduit to the suction valves of the compressor causing them to open and to remain open during the discharge stroke of the compressor cylinders, thereby to cause the compressor to cease to deliver compressed air through the discharge conduit 2. At the same time, said pressure from the receiver passes through the air conduit 4 into the air pressure chamber 3'1 and onto the piston 33 causing it to move within the chamber, which movement is transmitted through the piston rod 32 to cause the front valve head 35 to seat, thereby to close the compressed air discharge conduit 2 and to prevent the return flow of compressed air from the receiver into the compressed'air inlet chamber [5 and thence back to the compressor.

Thereafter the pressure of the return flow of compressed air from the receiver into the compressed air discharge chamber [6 acts upon the rear face of the front valve head 35 tohold the same in seated position until the cycle first above described is repeated, atmospheric pressure again being restored to the air pressure chamber 37, the compressor again starting to deliver compressed air, and the pressure of the compressed air delivered into inlet chamber l5 overcoming the pressure of the compressed air into discharge chamber Hi to unseat the front valve head 35 and to open the discharge conduit 2 to the receiver.

While the three-way release valve 1 operates in response to pressure within the receiver, as aforesaid, it is understood that it may additionally be operated manually or electrically in the usual manner and if the compressor is shut down completely at any time by stopping the compressor motor, the release valve 1 will be simultaneously ther, while by way of example the compressor was described above as a two-stage compressor, the invention is applicable to compressors of any number of stages.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. An air compressor system comprising a compressed air discharge conduit leading from a compressor to a receiver, a valve device operative to prevent the return flow of compressed air through said conduit from the receiver, said valve device comprising a valve seat in the conduit, a valve head movable to seated and unseated positions to close and open the conduit respectively, and normally held in unseated position by the pressure of compressed air delivered through the conduit from the compressor, and an air pressure chamber having a pressure responsive control means operatively connected to the valve head, means for admitting atmospheric pressure to said chamber while the compressor is delivering air to the receiver and for supplying compressed air from the receiver when the compressor ceases to deliver air, said control means being inactive so long as subjected to atmospheric pressure and being operative in response to the pressure of the compressed air from the receiver to seat the valve head, thereby to close the conduit.

2. An air compressor system comprising a compressed air discharge conduit leading from a compressor to a receiver, a valve device operative to prevent the return flow of compressed air through said conduit from the receiver, said valve device comprising a valve seat in the conduit, a valve head movable to seated and unseated positions to close and open the conduit respectively, and normally held in unseated position by the pressure of compressed air delivered through the conduit from the compressor, and an air pressure chamber, a piston slidable within the chamber, a rod connecting the piston with the valve head for movement therewith, means for admitting atmospheric pressure to said chamber while the compressor is delivering air to the receiver and for supplying compressed air from the receiver on to the piston when the compressor ceases to deliver air, said piston sliding freely within the chamber so long as subjected to atmospheric pressure and being operative in response to the pressure of the compressed air from the receiver thereon to seat the valve head, thereby to close the conduit.

3. An air compressor system comprising a compressed air discharge conduit leading from a compressor to a receiver, a suction valve in the compressor which when open provides free communication between the interior of the compressor and the atmosphere, an unloader pressure conduit leading from the receiver to the suction valve, and a three-way release valve in the unloader pressure conduit normally opening said unloader conduit between said valve and the suction valve to the atmosphere and operative in response to a predetermined maximum pressure within the receiver to provide communication between the unloader pressure conduit and suction valve, the suction valve being operative to open in response to said predetermined pressure, and a valve device operative to prevent the return flow of compressed air through the discharge conduit from the receiver, said valve device comprising a valve seat in the discharge conduit, a valve head movable to seated and unseated positions to close and open the discharge conduit respectively, and normally held in unseated position by the pressure of compressed air delivered through the conduit from the compressor, and an air pressure chamber having a pressure responsive control means operatively connected to the valve head, and a conduit leading from the chamber to the unloader pressure conduit on the suction valve side of the threeway release valve and providing communication therebetween, said control means being inactive so long as subjected to the atmospheric pressure from the unloader conduit and being operative in response to said predetermined maximum pressure from the unloader conduit to seat the valve head, thereby to close the conduit.

MALCOLM J. CADY.

No references cited. 

